What is a square in roofing? 100 square feet, bundles per square, and how to count them
A square is 100 square feet of roof area. A roof's squares are its area on the slope divided by 100: the footprint, overhangs included, times the pitch's area factor. A 2,000 sq ft roof is 20 squares; with 10% waste, 22 squares, and most shingles come three bundles to a square (GAF).
Anthony Hicks30+ years in construction. Updated November 5, 2026.
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A square is 100 square feet
Roofers measure and price roofs by the square: 100 square feet of roof, a 10 by 10 foot patch (GAF). Shingles, underlayment and the labor to put them on are all priced per square, so a roof’s size in squares is the first number on a roofing estimate.
Counting a roof’s squares
- Measure the footprint at the roof’s edge: the house’s length and width plus the overhang on every side.
- Multiply by the pitch’s area factor, since a sloped roof is bigger than the ground under it.
- Divide by 100 for squares.
- Add waste: about 10% on a plain gable, about 15% on a hip roof, more where valleys and dormers cut it up.
A 50 by 30 foot house with 12 inch overhangs is 52 by 32 at the edge, 1,664 square feet. At 6/12, the factor is 1.118: 1,664 × 1.118 = 1,860 square feet, or 18.6 squares; with 10% waste, 20.5 squares to buy.
| Pitch | Area factor |
|---|---|
| 4/12 | 1.054 |
| 6/12 | 1.118 |
| 8/12 | 1.202 |
| 10/12 | 1.302 |
| 12/12 | 1.414 |
The guide to finding a roof’s pitch has every pitch, and the roofing calculator does the whole count.
Squares to bundles
Most 3-tab and architectural shingles come three bundles to a square; some heavier shingles come four or five, and the wrapper says (GAF). At three a square, 20.5 squares is 62 bundles.
Squares to cost
A typical one-story house of 1,800 sq ft has about 22 squares of roof on a 6/12 gable, and in architectural shingles comes to about $11,800 to $17,400, overhead, profit and tax included. The roof replacement cost guide has it by state.
Common questions
How many square feet in a square of shingles?
100 square feet of roof.
How many squares is a 2,000 sq ft roof?
20 squares, or 22 with 10% waste. If 2,000 square feet is the house, not the roof, the roof is bigger: multiply the footprint with its overhangs by the pitch’s factor first.
How many bundles in a square?
Three for most shingles; heavier ones can take four or five (GAF).
Why do roofers use squares?
It simplifies the estimate: shingles, underlayment and labor are all priced per square (GAF).